1. Field of the Invention
This invention relates to circuit breakers for protecting electric power circuits. More particularly, it relates to circuit breakers with a set of secondary contacts, which are remotely controllable through a latchable operator, such as a magnetically latchable solenoid and which include a by-pass lead that by-passes the latchable operator.
2. Background Information
Circuit breakers provide over-current protection for preventing personal injury and property damage. A loadcenter or panelboard receives electrical power from the utility company transformer and routes the electrical power through a main circuit breaker and then through branch circuit breakers to designated branch circuits, each supplying current to one or more electrical loads. The circuit breakers are designed to interrupt the electrical current if it is excessive or outside the design limits of the conductor and loads, to reduce the risk of injury and damage.
Circuit breakers used in residential and light commercial applications are commonly referred to as miniature circuit breakers because of their limited size. Such circuit breakers typically have a pair of separable contacts opened and closed by a spring biased operating mechanism. A thermal-magnetic trip device actuates the operating mechanism to open the separable contacts in response to persistent overcurrent conditions and to short circuits. Usually, circuit breakers of this type for multiple circuits within a residence or commercial structure are mounted together within the load center or panel board.
In some applications, it has been found convenient to use the circuit breakers for other purposes than just protection, for instance, for load shedding. It is desirable to be able to perform this function remotely, and even automatically, such as under the control of a computer. However, the spring biased operating mechanisms are designed for manual reclosure and are not easily adapted for reclosing remotely. In any event, such operating mechanisms are not designed for repeated discretionary switching operation over an extended period of time.
As disclosed in U.S. Pat. Nos. 5,301,083 and 5,373,411 which describe remotely operated circuit breakers, miniature circuit breakers have been developed with a second pair of contacts in series with the main separable contacts. The main contacts still interrupt the overcurrent, while the latching contacts perform the discretionary switching operations. The latching contacts are controlled by a solenoid, which is spring biased to close the contacts. The solenoid can be controlled from a remote location.
The disadvantage of such a remote control circuit breaker is that, while the operator may only desire to open the circuit for one device, the entire circuit will be open once the solenoid is activated. Often, it is desirable to have some power supplied to an area controlled by the remote control circuit breaker. For example, a factory uses a remote control miniature circuit breaker to provide electricity to a device having a motor and a computer for diagnostics, e.g., the computer tracks performance of the motor. The miniature circuit breaker is used to turn the motor off and on by actuating the solenoid. If only one circuit is available, the diagnostic computer will be turned off when the motor is turned off, thus limiting the usefulness of the computer. That is, if the motor develops a problem, it must be turned off. Turning off the motor also turns off the computer. Using the prior art circuit breakers, the only configuration that allows the motor to be off and the computer to remain in operation requires the use of two separate circuits. Use of multiple circuits for a single location can be expensive and inconvenient. Additionally, each circuit requires its own breaker to detect a fault.
There is, therefore, a need for a remote control circuit breaker that will open the entire circuit upon a fault, but which has a load terminal that bypasses the circuit operated by the remote control.
There is a further need for such circuit breaker that is compatible with existing load centers and panel boards.
There is a further need for such circuit breaker that is easily manufactured.
These needs, and others, are satisfied by the invention, which provides a remotely controllable circuit breaker, which includes a latching solenoid to open and close a latching contact terminal and a by-pass terminal. The circuit for the latching contact terminal passes through the main contacts and the latching contact. The circuit for the by-pass wire only passes through the main contacts. The main contacts can be manually opened or opened via the thermal-magnetic trip device. The latching contact is opened by operation of the solenoid.
Thus, the invention provides a circuit breaker having two load terminals or a load terminal and a wire lead terminal. Both terminals are in electrical communication with the main contacts. Therefore, whenever a fault occurs and the main contacts are tripped, or when the main contacts are intentionally opened, both terminals are de-energized. When the main contacts are closed and the latching contact is opened, however, only the latching contact terminal is de-energized.